Well it is a hard one. I will tell you what we do but it hasn't stopped the behaviour totally so I am not sure that it works short term but I am banking on the long term . For us hitting is an immediate time out. If DS can't control his body then we have to keep ourselves safe and that is how we explain it to him. Often he needs to space to calm down anyway. Hurting other people is not acceptable at all. If we were out (e.g. at a play centre) he would get one warning that if he does it again we are leaving immediately, and then we follow through with that as we also have a responsibility to the other kids there that DS won't hurt them. It is tough but what can you do?!? I try my best to stay really calm and explain that what we are doing is a direct consequence of him hurting us/other people and that it is ok to be angry but it isn't ok to hurt people, even when we are angry. When he controls his body then he can join in. It sounds great in theory and sometimes it is hard to stay calm (especially when you have done it for the hundredth time that week) but I guess like I said I am hoping that in the long term he will learn the rule and copy our behaviour of staying calm and talking about what we need rather than hitting.